Elimination of electric-pop noise in MR/GMR device

ABSTRACT

The invention relates to a magnetic recording head comprising: a bottom shield; a top shield; and AMR device with MR and SAL separated by a thin insulating layer; a first insulting gap layer between said bottom shield and said AMR; a second insulating gap layer between said AMR and said top shield; a conductive layer contact at one end region of said MR and SAL. Furthermore, magnetic recording heads with GMR device free of electric-pop noise also are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. patentapplication Ser. No. 10/317,878, filed on Dec. 12, 2002, which is adivisional application of U.S. patent application Ser. No. 09/265,083,filed on Mar. 9, 1999, now issued as U.S. Pat. No. 6,583,971, and isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to an active devicecapable of converting an electrical signal into a voltage, morespecifically, to a magnetic recording head consisting of either ananisotropic magneto-resistive (hereinafter referred as AMR) or giantmagneto-resistive (hereafter referred as GMR) sensor along with aninsulation spacer and magnetic shields.

[0004] 2. Description of the Related Art

[0005] As is well known in the field, the insulating spacer in AMR/GMRrecording heads is becoming thinner and thinner in order to increase alinear recording density. Inevitably, we are facing electric-pop noiseresulting from the thinner spacer. For high manufacturing yield andreliability of electric and magnetic performance, such electric-popnoise must be eliminated.

[0006] U.S. Pat. No. 3,864,751 entitled “Induced Bias Magneto-resistiveRead Transducer” issued to Beaulier and Napela, on Feb. 4, 1975 proposedthat a soft-adjacent magnetic transverse bias layer (hereinafterreferred to as “SAL”) is isolated from a magneto-resistive device(referred to as MR hereinafter). The patent did not reveal any methodshow to make it. Another key point is that the MR and SAL areelectrically isolated. In the prior art described by Beaulieu et al.,electric-pop noise is present if a thinner insulating spacer (<150 Å),such as Al₂O₃, is used. Otherwise, the devices would need a thicker SALto bias the MR if a thicker insulator spacer (2-400 Å) were used. Thereare two problems associated with the latter case. Firstly, the SAL cannot be easily saturated by a current in the MR and an antiferromagneticpinning layer must be used to pin the SAL so that the SAL magnetizationis perpendicular to the current direction. In this case, the deviceprocess becomes very complicated and it also renders designs lessextendible to a narrower shield to shield spacing for higher densityrecording.

[0007] The SAL has a function as a shunt bias layer in SAL biased AMRdevices. When the MR and SAL are spaced by electric conductingmaterials, such as Ta, the SAL and MR devices have the same electrictrack width. These 15 configurations have been disclosed in U.S. Pat.No. 4,663,685 issued in 1987, to C. Tsang, U.S. Pat. No. 4,639,806issued in 1987 to T. Kira, T. Miyagachi, and U.S. Pat. No. 5,108,037issued to M. Yoshikawa, M. T. Krounbi, O. Voegeli and P. Wang.

SUMMARY OF THE INVENTION

[0008] Accordingly, one objective of this invention is to provide an AMRdesign with a thin insulating spacer free of electric-pop noise.

[0009] Another objective is to provide a SAL biased AMR product using aninsulated spacer.

[0010] A further objective of this invention is to provide an electricactive device free of electric-pop noise over an insulating spacer onthe top of an electric conductor.

[0011] Still another objective of this invention is to provide a designto eliminate electric-pop noise in GMR magnetic recording heads with athin insulating spacer.

[0012] In accordance with one aspect of the present invention, amagnetic recording device comprising:

[0013] an anisotropic magnetoresistive (MR) sensing layer;

[0014] a soft-adjacent magnetic transverse bias layer (SAL);

[0015] an insulating layer arranged between said magnetoresistive layerand said magnetic transverse bias layer;

[0016] a conductive layer contacting electronically both saidmagnetosensitive layer and said magnetic bias layer at at least one endregion of said SAL element.

[0017] In accordance with another aspect of the present invention, amagnetic recording device comprising:

[0018] a first shield;

[0019] a second shield;

[0020] a GMR device;

[0021] a first insulating gap layer between said GMR and one of saidshields;

[0022] a second insulating gap layer between said GMR and another ofsaid two shields;

[0023] a conductive layer contacting electrically said GMR device toeither one of said shields.

[0024] In accordance with one aspect of the present invention, amagnetoresistive device comprising:

[0025] a magnetosresistive layer;

[0026] a soft-adjacent magnetic transverse bias layer (SAL);

[0027] an insulating layer arranged between said magnetosresistive layerand said magnetic transverse bias layer;

[0028] a conductive layer contacting electrically both saidmagnetosresistive layer and 15 said magnetic bias layer at at least oneend region of said SAL element.

[0029] In accordance with a further aspect of the present invention, ahard disk driver is provided with the magnetoresistive device.

[0030] Compared to the prior art by Tsang, Kire et al and Kroumbi et al,this invention provides an AMR sensor with much improved signal. Thesignal improvement can be as much as 90% provided that the same MR/SALdevice and operating current are used for the device.

[0031] Other objects, features and advantages of the present inventionwill become readily apparent from the following description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

[0033]FIG. 1a is a diagram of a preferred embodiment of the invention,

[0034]FIG. 1b is a cross-section view taken along line AA indicated inFIG. 1a,

[0035]FIG. 2 is a diagram of an alternative embodiment of the invention,

[0036]FIG. 3 shows electric-pop test results before and after MR and SALare connected by microfabrication,

[0037]FIG. 4 shows an extension to prevent a GMR device fromelectric-pop noise due to discharge between the GMR device and shields.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0038] Embodiments according to the present invention will be describedin the following.

[0039]FIG. 1a is a diagram of a first preferred embodiment of theinvention. As shown in this figure, MR layer 10 and SAL 30 are separatedby a thin insulated spacer layer 20, and are electrically connected atthe ends of the MR element. An active region 10 of the MR device couldbe either a NiFe film or a composite layer, such as TaN/NiFe/TaN. NiFe,thickness ranges from 50 to 400 Å. Side regions 12 and 14 of the MRelement make electric contact with longitudinal bias layer and leadlayer 40 and 42. End regions 16 and 18 of the MR element are connectedto the end regions 32, 34 of SAL by leads. The length of MR element andSAL ranges from 2 to 20 μm. Insulating spacing layer 20 is made ofinsulating materials, such as Al₂O₃, AlON and SiO₂, and the typicalthickness of insulating spacing layer varies from 50 to 200 Å.Soft-adjacent layer (SAL) 30 can be made of NiFe, NiFeCr, NiFeRh. Themoment ratio of SAL 30 to MR layer 10 ranges from 0.6 to 1.0.

[0040] In FIG. 1a, longitudinal bias layer 40 can be made ofanti-ferromagnetic materials, such as NiMn, FeMn, PtPdMn, IrMn and PtMn.Lead layer 42 can be made of Ta, W or Ta/Au/Ta. Longitudinal bias layer40 and lead layer 42 extend coverage on top of the MR element 10 andelectrically contact with MR element 10 through side regions 12 and 14,respectively. Therefore, the electric track width of the MR element isdefined by active region 10 as longitudinal bias layer 40 and lead layer42 have much higher electric conductivity than the MR layer.

[0041] On the other hand, longitudinal bias layer 40 and lead layer 42electrically contact with SAL layer 30 through side surfaces 32 and 34,respectively. Therefore, the electric track width of the SAL element isentire element width.

[0042] Now refer to FIG. 1b that shows cross-section view taken alongline AA indicated in FIG. 1a. Function of insulator films 50 is toprevent electric connection from MR 10 to SAL 30. Numeral 60 designatesan air bearing surface (ABS).

[0043] In the following drawings, similar parts to those in FIG. 1 aredesignated by the same numerals as those used in FIG. 1. FIG. 2 shows analternative embodiment of the present invention. MR layer 10 and SAL 30are separated by a thin insulating spacer layer 20. MR layer 10 and SAL30 are electrically connected at only one end region of the MR element.In this embodiment, no electric current passes through the SAL element.However, the whole SAL element is in an equal electric potential to thatof one side of the MR element. One side region of the longitudinal biaslayer and the leader layer does not electrically contact with acorresponding SAL end region. Insulator films 52 are electricallyconnected between MR layer 10 and SAL 30 at one end of the trilayerdevice.

[0044]FIG. 3 shows test results of the electric-pop noise before andafter connection of MR layer 10 and SAL 30 under test conditions:trigger level=75 μV, threshold level=(Noise amplitude of Is=5 mA)+60 μV,and read current=12 mA.

[0045]FIGS. 3a and 3 b show electric-pop noise spectra of the devicebefore edge shorting of the MR and SAL element, and FIGS. 3c and 3 dshow the same of the device after edge shorting of the MR and SALelement.

[0046]FIG. 4 shows an extension to prevent a GMR device fromelectric-pop noise due to discharge between the GMR device and shields.

[0047]FIG. 4a is a diagram of a GMR device that is electrically shortedto a bottom shield to prevent electric-pop noise due to static dischargebetween the GMR device and a bottom shield.

[0048]FIG. 4b is a diagram of a GMR device that is electrically shortedto a top shield to prevent electric-pop noise due to static dischargebetween the GMR device and a top shield.

[0049] In FIGS. 4a and 4 b, reference numeral 60 designates a GMR activedevice, the GMR device including a spin-valve, GMR multilayer, andspin-dependent tunneling device, and numerals 62 and 64 designate alongitudinal bias layer and a lead layer, respectively. Electric contact66 is provided between one side of lead layer 64 and of longitudinalbias layer 62 and the bottom shield 70. Bottom and top shields 70 and 80are made of soft magnetic materials, such as NiFe. Gaps 72 and 74 arefilled with electrically insulating materials, such as Al₂O₃, AlNO, AlN,and vary from 250 to 2000 Å in thickness. Electric contact 68 isprovided between one side of lead layer 64 and of longitudinal biaslayer and top shield 80.

[0050] Operational principle of the present invention is explained asfollows.

[0051] Signal amplitude of the AMR device is given by equation:$\begin{matrix}\begin{matrix} {{\Delta \quad V_{pp}} = {{{MrW}*J_{MR}*\Delta \underset{\_}{\rho*R_{SAL}*( \sin^{2} }\theta} - {\sin^{2}\theta_{0}}}} ) \\{\quad ( {R_{MR} + R_{SAL}} )}\end{matrix} & (1)\end{matrix}$

[0052] where:

[0053] ΔV_(pp): peak-to-peak amplitude (V),

[0054] MrW: MR read track width (μm),

[0055] J_(MR): current density passing through the MR device film(A/m²),

[0056] Δρ: magnetoresistive coefficient of resistivity of the MR layer$\frac{R_{SAL}}{( {R_{MR} + R_{SAL}} )}:\quad \text{voltage shunting factor,}$

[0057] R_(MR): sheet resistance of the MR layer (Ω),

[0058] (R_(MR)+R_(SAL)): sheet resistance of the SAL layer (Ω), and

[0059] (sin²Θ-sin²Θ₀): sensitivity function of the MR device.

[0060] For the same operating current I, there is a signal enhancementby a factor of square of (R_(MR)+R_(SAL))/R_(SAL) comparing an AMRdevice without a current flowing through SAL to that with a currentshunting through the SAL. In a typical AMR device, the shunt factorR_(SAL)/(R_(MR)+R_(SAL)) is as much as 0.7.

[0061] In the case of a SAL electrically isolated from the MR element,the SAL is electrically floating, which could result in electric-popnoise due to static discharge between the MR and SAL. In the inventionillustrated in FIG. 1, we let a small percentage of current flow throughthe SAL. The way to achieve it is to provide electric contact to the SALat the end of the element. With such configuration, the SAL is no longerelectrically floating as there is a small amount of current flowingthrough the SAL. The shunting factor is determined by equation:$\begin{matrix}\frac{R_{SAL}*L_{SAL}}{{R_{MR}*W_{MR}} + {R_{SAL}*L_{SAL}}} & (2)\end{matrix}$

[0062] where:

[0063] R_(SAL): sheet resistance of the SAL,

[0064] R_(MR): sheet resistance of the MR layer,

[0065] L_(SAL): length of the SAL, and

[0066] W_(MR): electric trick width of the MR layer.

[0067] We can tune the current ratio by simply adjusting element heightand length. For reference, current MR/SAL sheet resistance ratio isabout 3/7. We can get 2% of current flowing through the SAL by settingwidth of the MR element at 20 μm assuming that our physical read trackwidth is at 1 μm. This shunt ratio renders such a device have muchhigher signal than that of conventional SAL-biased AMR heads with aconducting spacer.

[0068] An alternative approach taught in FIG. 2 is to electricallyconnect one end of the SAL to the MR element. In this case, the SALlayer keeps the same electrical potential as that of one terminal of theAMR device and is no longer electrically floating. The advantage of thisapproach is to eliminate the current shunting through the SAL whilepreventing the SAL from electrically floating. By doing this, we caneffectively eliminate charges building up in the SAL so that theelectric-pop noise in the MR device is prevented.

[0069] Similar concept is used to short an SV (spin valve) GMR device toeither a top or bottom shield. By doing this, we can prevent theelectric-pop noise due to static discharge between the GMR device andshields. It must be pointed out that such electric-pop noise is afundamental technology challenge for future higher density recording.

[0070] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details, and representativedevices, shown and described herein. Accordingly, various modificationsmay be made without departing from the spirit or scope of the generalinventive concept as defined by the appended claims and theirequivalents.

What is claimed is:
 1. A magnetic recording head, comprising: amagnetoresistive layer having a first end and a second end; asoft-adjacent magnetic transverse bias layer (SAL) having a first endand a second end; an insulating layer arranged between saidmagnetoresistive layer and said SAL; a first conductive layerelectrically contacting said first end of said magnetoresistive layerand said first end of said SAL; a second conductive layer electricallycontacting said second end of said magnetoresistive layer and saidsecond end of said SAL; the magnetoresistive layer supporting a firstcurrent path between the first and second conductive layers; and the SALsupporting a second current path between the first and second conductivelayers; wherein the second current path is substantially longer than thefirst current path.
 2. The magnetic recording head of claim 1, whereinsaid first current path passes through an active region in saidmagnetoresistive layer.
 3. The magnetic recording head of claim 2,wherein said first conducting layer includes an extending portion on atop surface of said magnetoresistive layer, and said second conductinglayer includes an extending portion on said top surface of saidmagnetoresistive layer, said active region being formed between saidfirst conducting layer extending portion, said magnetoresistive layer,and said second conducting layer extending portion.
 4. The magneticrecording head of claim 1, wherein thickness of said magnetoresistivelayer is more than 50 Å and less than 400 Å.
 5. The magnetic recordinghead of claim 1, wherein thickness of said SAL is less than 500 Å, andthe moment ratio of said SAL to said magnetoresistive layer ranges from0.6 to 1.0.
 6. The magnetic recording head of claim 1, wherein saidfirst conductive layer comprises a longitudinal bias layer and a leadlayer.
 7. The magnetic recording head of claim 1, wherein said secondconductive layer comprises a longitudinal bias layer and a lead layer.8. The magnetic recording head of claim 1, wherein said insulating layerranges from 50 Å to 200 Å in thickness.
 9. The magnetic recording headof claim 8, wherein said insulating layer is formed of Al₂O₃.
 10. Themagnetic recording head of claim 1, wherein said SAL comprises amagnetically soft film layer pinned by antiferromagnetic films.